kinsell wrote on 11/14/2018 12:55 PM:
On 11/14/18 9:03 AM, wrote:
On Tuesday, November 13, 2018 at 11:11:52 PM UTC-5, kinsell wrote:
On 11/13/18 6:08 PM, bruce... wrote:
Mark, When K2 was fairly new on the market I contacted them asking if Battery
Tender Jr. is okay and safe, they replied that it is perfectly okay and nearly
the same as their charger. I also contacted Battery Tender Jr. with the
reverse question and they said the BTJr is fine for LiFePO4. I used the BTJr
for years on my K2* with no issues. They're about $25 on internet sites.


Have you measured the amount of charge you're getting into the K2's?* It
will be considerably less than the rated amount due to using a lead-acid
charger.

Also, if K2 has cell balancing capability, it won't be used because your
Battery Tender doesn't put out enough voltage to make it work.

Many simple lead-acid chargers reach up to around 14.2-14.8 volts.* That voltage
would suffice to charge an LFP battery to well above 90% capacity if it stays
there for a while.* If it quickly shifts to "float" at 13.5V or so then it won't
do well in charging LFP.* So simpler is better in this case.* Measure what your
charger does.* And disconnect it after several hours, don't leave it on "float".


Hate to break this to you, but at $24, the Battery Tender Junior is one of the
cheapest chargers on the market, and is fully featured with a float mode.

14.2 volts wouldn't begin to charge an LFP to "well over 90%" as you claim.* If
you found a charger that delivers 14.8 volts under load, then it would overcharge
an SLA and would be considered defective.

If you're going to spend big bucks for an LFP, you ought to get a proper charger
for it.* Still waiting to hear just how much charge the K2's got in them from a BTJ.

Bienno Power has a $25, 12V/4A LiFePO4 charger. I'd trust that over a BT Jr, and
it's the same price.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf